Description:
The availability of €smart€ materials that change their properties, such as mechanical strength or permeability, in response to specific physical or chemical cues would revolutionize biotechnologies ranging from targeted drug delivery to medical diagnostics. An emerging strategy for developing such materials is to use natural biopolymers, such as DNA, to build novel architectures with desired properties. Specifically, these biopolymers can be engineered into tunable, self-assembling, target-responsive networks. Significant tradeoffs, however, likely exist for such materials between their thermodynamic stability and their kinetic responsiveness (i.e., stable materials respond only very slowly to their cues), which could limit their utility. Here we explore this tradeoff in a biopolymer hydrogel network consisting of Y-shaped monomers and aptamer (i.e., a molecular cue-binding DNA strand) crosslinkers, which allow the hydrogel to disassemble in the presence of its molecular cue. Specifically, we explore the extent to which changes in the overlapping base-pairing regions at the aptamer-monomer junction, such as overlap length and the inclusion of mismatches, affect hydrogel mechanics, stability and dissociation kinetics. This is achieved by directly monitoring conformational changes in the crosslinker (i.e., from active to inactive) in response to target ligand via FRET, and observing bulk properties of the gel through passive rheology of ~200-3000 nm beads placed within the gel. Our goal is to discern the design parameters that will lead to optimal material stability and responsiveness.